Method for the production of a continously-cast precursor

ABSTRACT

The invention relates to a process for producing a continuously cast primary product, in particular broad slabs, having a thickness of the primary product D&gt;100 mm and a width of the primary product B=2700 mm to 3500 mm at a casting rate v c &lt;2 m/min in a continuous-casting plant, and to a continuous-casting plant for producing these products and to a submerged nozzle therefor.  
     To achieve uniform solidification conditions for the cast strand and uniform melting and distribution conditions for the casting powder, it is proposed that the molten material leaves the submerged nozzle through opposite outlet openings with a momentum which is directed toward the narrow side walls of the permanent mold, and for a defined width:thickness ratio of the primary product, as a function of the ratio of the velocity of the molten material in the core cross section of the submerged nozzle (v k ) to the casting rate (v c ), design values for the width (b) of the submerged nozzle and the height (h) of the lateral outlet opening of the submerged nozzle are selected in such a way that a uniform strand shell is formed in the casting direction and peripheral direction along the wide side walls and narrow side walls of the permanent mold.

[0001] The invention relates to a process for producing a continuouslycast primary product, in particular broad slabs, having a thickness ofthe primary product D>100 mm and a width of the primary product B=2700mm to 3500 mm at a casting rate v_(c)<2 m/min in a continuous-castingplant, in which molten material, preferably molten steel, from areservoir is introduced via a submerged nozzle into a permanent mold,which is formed by wide side walls and narrow side walls, and theprimary product, which has partially solidified in the permanent moldand has a liquid core and a solidified strand shell, is continuouslywithdrawn from the permanent mold and cooled, to a continuous-castingplant for producing a continuously cast primary product and to asubmerged nozzle for use in this continuous-casting plant.

[0002] When the submerged-casting process is used in continuous casting,it is customary for the molten material to be introduced from areservoir, generally a tundish, through a submerged nozzle which iscoupled thereto, into an oscillating permanent mold below a bath levelwhich is covered with casting powder. This procedure can be carried outwithout problems for small permanent-mold cross sections, but, inparticular with permanent molds with a high width:thickness ratio, leadsto difficulties with the formation of an optimum permanent-mold flow andtherefore impairs uniform strand shell growth during the gradualsolidification of the molten material at the cooled permanent-mold wall.

[0003] DE-C 197 24 232 has already disclosed a process for producingprimary products in the form of slabs in a continuous-casting plantusing the principle described above. In this case, the molten materialis introduced into the permanent mold through a submerged nozzle whichlies below the bath level, is open at the bottom in the castingdirection and widens out in the shape of a funnel toward the narrow sidewalls of the permanent mold. If the dimension rule given in claim 2 ofDE-C 197 24 232 for the submerged nozzle in terms of its width (b) isapplied to the widths (B) of the primary product or of the permanentmold of from 2700 mm to 3500 mm which are provided for according to theinvention, the result is submerged nozzle widths (b) of approximately385 mm to 2250 mm, which cannot be produced from refractory materialswith the durability when used at high temperatures which is required forlong-term operation. Moreover, such wide submerged nozzles exacerbatethe known problems with the gap flow between submerged-nozzle wall andwide side wall of the permanent mold.

[0004] DE-C 196 47 363 has disclosed a submerged nozzle which issuitable for use for the continuous casting of slabs and in which themolten material emerges below the bath level through outlet openings,which lie laterally opposite one another, toward the narrow side wallsof the permanent mold. An essential feature of this submerged nozzle isthe constant distance between its outer wall and the strand shell whichis formed along the wide side wall. This means that this submergednozzle is suitable for a width:thickness ratio of the cast strand or ofthe permanent-mold cross section of at most 8. However, if thewidth:thickness ratios are higher, this submerged nozzle cannot ensure apermanent-mold flow which creates uniform solidification conditions.

[0005] During the continuous casting of primary products with highwidths, despite standard casting rates of 1.0 m/min to 1.2 m/min, veryhigh steel throughputs of up to 4 to/min and above are reached. Inpractice, it has been found with these high steel throughputs that theswirl-forming flows which form in the permanent mold are very unstable.The guidance property of the permanent-mold chamber for this flowdeteriorates at increasing distance between the submerged nozzle outletopening and the narrow side wall. In addition, the emerging jet, onaccount of its high local flow velocity in the submerged nozzle andimmediately after it emerges from the submerged-nozzle outlet opening,on account of the resistance of the molten material and the high wallfriction along the permanent mold walls, is greatly decelerated and, onaccount of the reduced pressure between casting level and emerging jet,is diverted upward toward the casting level. A fluctuating, oscillatingbath movement, which has an adverse effect on the product quality, isvisually observed.

[0006] This unfavorable formation of the flow conditions is illustratedin FIG. 1 on the basis of a filament of flow. In the region between thesubmerged nozzle and the permanent-mold narrow side wall, the emergingjet hits the bath surface, where it splits into two partial jets. Thisphenomenon leads to a lack of uniformity in the melting of the castingpowder at the bath surface and to local adverse effects on the slidingcharacteristic between stand and permanent-mold wall. When conventionalsubmerged nozzles are used to cast broad slabs, it is difficult for theabove-mentioned reasons, to produce a favorable and stable flow in thepermanent mold.

[0007] Therefore, it is an object of the invention to avoid thesedrawbacks which have been described and to propose a process forproducing a continuously cast primary product, as well as thecontinuous-casting plant required for this process and a submergednozzle for use in this continuous-casting plant, in which uniformsolidification conditions for the strand and uniform melting anddistribution conditions for the casting powder are ensured even for highcast widths. Furthermore, by means of a defined supply of steel throughthe submerged nozzle, it is intended to produce a stable system ofswirling in the permanent mold which is formed by two large, roundswirls directed upward. Furthermore, it is an object of the inventionnot to allow any lateral deflection of the immerging jet, and inparticular to prevent the immerging jet from coming into contact withthe bath level prematurely.

[0008] According to the invention, this object is achieved by a processwhich is characterized in that the molten material leaves the submergednozzle through opposite outlet openings with a momentum which isdirected toward the narrow side walls of the permanent mold, and for adefined width:thickness ratio of the primary product, as a function ofthe ratio of the velocity of the molten material in the core crosssection of the submerged nozzle (v_(k)) to the casting rate (v_(c)),design values for the width (b) of the submerged nozzle and the height(h) of the lateral outlet opening of the submerged nozzle are selectedin such a way that a uniform strand shell is formed in the castingdirection and peripheral direction along the wide side walls and narrowside walls of the permanent mold.

[0009] Optimum conditions for the formation of the strand shell areestablished if the submerged nozzle in relation to the permanent moldsatisfies the following conditions$\frac{h}{B} = {{\frac{9}{5}\psi} + {\frac{1}{5}\frac{D}{B}}}$

[0010] and $\frac{b}{h} = {1.9 - 2.0}$

[0011] and a numerical ratio ψ, which sets the relationship of thevelocity of the molten material in the core cross section of thesubmerged nozzle (v_(k)) to the casting rate (v_(c)), is determinedaccording to the following condition$\psi = {0.1\left( \frac{B}{D} \right)^{- 0.7}}$

[0012] in which:

[0013] B=width of the primary product (mm)

[0014] D=thickness of the primary product (mm)

[0015] b=width of the submerged nozzle (mm)

[0016] h=height of the lateral outlet opening of the submerged nozzle(mm)

[0017] ψ=numerical ratio (no dimensions).

[0018] For the width:thickness ratios selected, the above conditionresults in ψ values of from 0.011 to 0.015. These values express thefact that for optimum flow conditions low flow velocities in thesubmerged nozzle are required, and according to the invention areachieved by means of large core and outlet cross sections at thesubmerged nozzle. The reduction in the flow velocity avoids considerablelateral deviations of the emerging jet which are caused by the reducedpressure between the emerging jet and the casting level.

[0019] These measures make it possible to form a stable swirling systemwith large, substantially round swirls which turn upward, as illustrateddiagrammatically in FIG. 2 for the half of the permanent-mold chamberwhich lies to the left of the submerged nozzle on the basis of afilament of flow. The swirl diameter approximately corresponds to halfthe strand width. The jet-outlet angle of approximately 40 to 45°required for this purpose is achieved by means of the great height (h)of the lateral outlet opening of the submerged nozzle. As a result, theknown phenomenon whereby the emerging jet is diverted toward the castinglevel after only a short distance when there is considerable flowdiversion in the submerged nozzle (small outlet angle) is reduced. Thegreat height (h) of the lateral outlet opening means that a flow whichis subject to little or no rotation is established.

[0020] Furthermore, the measures of the invention ensure that it ispossible to build up a system with very pronounced swirls. For thispurpose, the emerging jet which leaves the submerged nozzle must not bedecelerated excessively between the two permanent-mold wide sides. Thedecelerating action on the emerging jet is determined by wall friction,which forms through contact between the moving emerging jet and thestrand shell. Since the decelerating frictional force increases toapproximately the power of two with respect to the flow velocity, theoutlet velocity is according to the invention kept at a low level.

[0021] An advantageous application range for the process is provided ifthe primary product has a width:thickness ratio${\frac{B}{D} = {15 - 25}},$

[0022] preferably a width:thickness ratio $\frac{B}{D}$

[0023] of approximately 20.

[0024] For the proposed primary product cross sections, it is preferablefor the casting rate vc to be set to between 0.5 m/min and 1.5 m/min.

[0025] A continuous-casting plant according to the invention for theproduction of a continuously cast primary product, in particular ofbroad slabs, having a thickness of the primary product D>100 mm and awidth of the primary product B=2700 mm to 3500 mm at a casting rate ofv_(c)<2 m/min, comprising a permanent mold, which is formed by wide sidewalls and narrow side walls, a submerged nozzle which projects into thepermanent mold on the entry side and a reservoir for the moltenmaterial, and also devices which are arranged on the exit side of thepermanent mold for withdrawing, guiding and cooling the primary product,which has partially solidified in the permanent mold and has a liquidcore and a solidified strand shell is characterized in that thesubmerged nozzle includes outlet openings which lie opposite one anotherand in the operating position are directed toward the narrow side wallsof the permanent mold, in that the internal dimensions of the permanentmold at the level of the lateral outlet openings of the submerged nozzlesubstantially correspond to the dimensions of the primary product, andin that the width (b) of the submerged nozzle and the height (h) of thelateral outlet opening of the submerged nozzle are fixed in relation toa defined width:thickness ratio of the primary product or the permanentmold in such a way that the conditions$\frac{h}{B} = {{\frac{9}{5}\psi} + {\frac{1}{5}\frac{D}{B}}}$

[0026] and $\frac{b}{h} = {1.9 - 2.0}$

[0027] are fulfilled and a numerical ratio ψ which sets the relationshipbetween the velocity of the molten material in the core cross section ofthe submerged nozzle (v_(k)) to the casting rate (v_(c)) is determinedaccording to the following condition$\psi = {0.1{\left( \frac{B}{D} \right)^{- 0.7}.}}$

[0028] A continuous-casting plant of this type is particularly suitableif the primary product has a width:thickness ratio${\frac{B}{D} = {15 - 25}},$

[0029] preferably a width:thickness ratio $\frac{B}{D}$

[0030] of approximately 20.

[0031] To achieve an optimum jet outlet angle, the inner base of thesubmerged nozzle is designed to be inclined from the center of thesubmerged nozzle toward the outlet opening in the casting direction.Particularly favorable conditions are established if the inclination ofthe inner base of the submerged nozzle is from 10° to 20°, preferablyapproximately 15°.

[0032] A submerged nozzle according to the invention for use in acontinuous-casting plant for producing a continuously cast primaryproduct, in particular broad slabs, having a thickness of the primaryproduct D>100 mm and a width of the primary product B=2700 mm to 3500 mmat a casting rate of v_(c)<2 m/min, this continuous-casting plant havinga permanent mold, which is formed by wide side walls and narrow sidewalls and into which the submerged nozzle projects in operation ischaracterized in that the submerged nozzle has lateral outlet openingswhich lie opposite one another, and a continuous inner base, in that theinternal dimensions of the permanent mold at the level of the lateraloutlet openings of the submerged nozzle substantially correspond to thedimensions of the primary product, in that the width (b) of thesubmerged nozzle and the height (h) of the lateral outlet opening of thesubmerged nozzle are fixed in relation to a defined width:thicknessratio of the primary product or the permanent mold in such a way thatthe following conditions$\frac{h}{B} = {{\frac{9}{5}\psi} + {\frac{1}{5}\frac{D}{B}}}$

[0033] and $\frac{b}{h} = {1.9 - 2.0}$

[0034] are fulfilled and a numerical ratio v which sets the relationshipof the velocity of the molten material in the core cross section of thesubmerged nozzle (v_(k)) to the casting rate (v_(c)) is determinedaccording to the following condition$\psi = {0.1{\left( \frac{B}{D} \right)^{- 0.7}.}}$

[0035] An advantageous configuration is provided by the inner base ofthe submerged nozzle being designed to be inclined from the center ofthe inner base toward the outlet opening. The inclination of the innerbase of the submerged nozzle is 10° to 20°, preferably approximately15°. This significantly increases the tendency to form a turbulence-freeemerging jet. Only two outlet openings, which are of substantiallyrectangular design, are arranged at the submerged nozzle.

[0036] Further advantages and features of the present invention willemerge from the following description of two nonlimiting exemplaryembodiments, in which reference is made to the following figures, inwhich:

[0037]FIG. 1 diagrammatically depicts the permanent-mold flow when usinga submerged nozzle in the permanent mold of a continuous-casting plantaccording to the prior art,

[0038]FIG. 2 diagrammatically depicts the permanent-mold flow when usinga submerged nozzle in the permanent mold of a continuous-casting plantaccording to the invention,

[0039]FIG. 3a shows part of a longitudinal section through the submergednozzle according to the invention,

[0040]FIG. 3 shows the diagrammatic outline of permanent mold andsubmerged nozzle on section A-A through the submerged nozzle shown inFIG. 3a.

[0041] Steel continuous-casting plants for the production of broad slabsare generally known, are described in the literature and substantiallycomprise a tundish for holding the molten steel, from which the moltenmaterial is transferred via a submerged nozzle into an oscillatingpermanent mold. A partially solidified cast strand of steel is conveyedvertically downward out of the permanent mold, is cooled in a subsequentstrand-guidance section and is then diverted into a horizontalorientation. Then, the fully solidified cast strand is divided intoslabs by means of a flame-cutting machine, and the slabs are then fedfor further treatment.

[0042] The shaping of the cast strand takes place in an oscillatingcontinuous-casting permanent mold 1 which, as diagrammatically depictedin FIG. 3b, is formed by wide side walls 2, 3, which lie opposite oneanother, and narrow side walls 4, 5, which can be clamped between thewide side walls, it being possible for the narrow side walls 4, 5 to bedisplaced transversely to the casting direction in order to setdifferent strand widths (B). The inner surfaces of these walls form achamber which determines the format for the formation of a partiallysolidified cast strand which is discharged from the permanent mold asprimary product.

[0043] The invention is restricted to a process for producing a primaryproduct with a width B of from 2700 to 3500 mm and a thickness D>100 mmand to a continuous-casting plant having a permanent mold which hasthese cross-sectional dimensions. In the permanent mold itself, the caststrand is not subject to any significant deformation.

[0044] The molten material which is to be cast is introduced from areservoir which is not shown but is well known in casting plants of thistype, via a submerged nozzle 6 below the bath level 7 formed by themolten material in the permanent mold, through lateral outlet openings 8directed toward the narrow side walls 4, 5, into the continuous-castingpermanent mold 1. The molten material flows through the submerged nozzle6 in the vertical direction, which corresponds to the casting directionin the permanent mold, at the velocity v_(k) and, in the region of thecontinuous inner base 9 of the submerged nozzle 6, is diverted towardthe lateral outlet openings 8 and passes through them into thepermanent-mold chamber. The inner base 9 is designed to be inclined fromits center toward the outlet opening 8 in the casting direction. Thisinclination and the height (h) of the lateral outlet opening (8)determine the direction (the angle) of the emerging molten material andtherefore influence the flow which is formed. The submerged-nozzlethickness (d) is substantially determined by the thickness of theprimary product (D). The width (B) and the thickness (D) of the primaryproduct are fixed by production specifications. The result of this isthat the width (b) of the submerged nozzle, the height (h) of thelateral outlet opening of the submerged nozzle and the dimensionlessnumber ψ, which substantially describes the ratio of casting rate v_(c)and velocity v_(k) of the liquid jet in the submerged nozzle (core crosssection), can be selected as desired.

[0045] The value ψ in relation to the submerged nozzle geometrydetermines the velocity of the molten material in the submerged-nozzleoutlet cross section and is therefore crucial to the quality of thepermanent-mold flow. When casting medium-thick and wide slabs(width:thickness ratio of approximately 20), ψ values of 0.006 to 0.008are achieved with conventional submerged nozzles. Tests have shown thatto cast very wide cast strands with the same width:thickness ratio, itis necessary to reach ψ values of 0.011 to 0.015. This requires lowervelocities in the submerged nozzle, which are achieved by means of largecore and outlet cross sections.

[0046] Table 1 below illustrates these relationships for a primaryproduct thickness D=157 mm which is selected by way of example, withprimary product widths of B=2500 mm and B=3000 mm. The submerged nozzlesaccording to the invention are distinguished by the greater height h ofthe lateral outlet openings 8. TABLE 1 conventional inventive submergednozzle submerged nozzle B = 2500 mm ψ = 0.006-0.008 ψ =0.011-0.015$\frac{D}{B} = 0.628$

$\frac{h}{B} = {0.023 - 0.026}$

$\frac{h}{B} = {0.032 - 0.040}$

$\frac{B}{D} = 16$

h = 58-67 mm h = 81-99 mm B = 3000 mm ψ = 0.006-0.008 ψ = 0.011-0.015$\frac{D}{B} = 0.052$

$\frac{h}{B} = {0.021 - 0.025}$

$\frac{h}{B} = {0.030 - 0.037}$

$\frac{B}{D} = 20$

h = 63-75 m h = 91-112 mm

[0047]FIG. 1 diagrammatically depicts the formation of thepermanent-mold flow on the basis of a filament of flow when using aconventional submerged nozzle, the emerging jet coming into contact withthe bath surface in the region between submerged nozzle 6 andpermanent-mold narrow side wall 4 and there being divided into twopartial jets. By contrast, FIG. 2 shows the flow profile using asubmerged nozzle according to the invention, in which the flow is onlydivided into two partial streams in the region of the narrow side wall 4and forms two approximately circular swirls.

1. A process for producing a continuously cast primary product, inparticular broad slabs, having a thickness of the primary product D>100mm and a width of the primary product B=2700 mm to 3500 mm at a castingrate v_(c)<2 m/min in a continuous-casting plant, in which moltenmaterial, preferably molten steel, from a reservoir is introduced via asubmerged nozzle into a permanent mold, which is formed by wide sidewalls and narrow side walls, and the primary product, which haspartially solidified in the permanent mold and has a liquid core and asolidified strand shell, is continuously withdrawn from the permanentmold and cooled, characterized in that the molten material leaves thesubmerged nozzle through opposite outlet openings with a momentum whichis directed toward the narrow side walls of the permanent mold, and fora defined width:thickness ratio of the primary product, as a function ofthe ratio of the velocity of the molten material in the core crosssection of the submerged nozzle (v_(k)) to the casting rate (v_(c)),design values for the width (b) of the submerged nozzle and the height(h) of the lateral outlet opening of the submerged nozzle are selectedin such a way that a uniform strand shell is formed in the castingdirection and peripheral direction along the wide side walls and narrowside walls of the permanent mold.
 2. The process as claimed in claim 1,characterized in that the submerged nozzle in relation to the permanentmold satisfies the following conditions$\frac{h}{B} = {{\frac{9}{5}\psi} + {\frac{1}{5}\frac{D}{B}}}$

and $\frac{b}{h} = {1.9 - 2.0}$

and a numerical ratio ψ, which sets the relationship of the velocity ofthe molten material in the core cross section of the submerged nozzle(v_(k)) to the casting rate (v_(c)), is determined according to thefollowing condition$\psi = {0.1\quad \left( \frac{B}{D} \right)^{- 0.7}}$

in which: B=width of the primary product (mm) D=thickness of the primaryproduct (mm) b=width of the submerged nozzle (mm) h=height of thelateral outlet opening of the submerged nozzle (mm) ψ=numerical ratio(no dimensions).
 3. The process as claimed in claim 1 or 2,characterized in that the primary product has a width:thickness ratio$\frac{B}{D} = {15 - 25.}$


4. The process as claimed in claim 1 or 2, characterized in that theprimary product has a width:thickness ratio $\frac{B}{D}$

of approximately
 20. 5. The process as claimed in one of claims 1 to 4,characterized in that the casting rate v_(c) is set to between 0.5 m/minand 1.5 m/min.
 6. A continuous-casting plant for producing acontinuously cast primary product, in particular broad slaps, having athickness of the primary product D>100 mm and a width of the primaryproduct B=2700 mm to 3500 mm at a casting rate of v_(c)<2 m/min,comprising a permanent mold (1), which is formed by wide side walls (2,3) and narrow side walls (4, 5), a submerged nozzle (6) which projectsinto the permanent mold on the entry side and a reservoir for the moltenmaterial, and also devices which are arranged on the exit side of thepermanent mold for withdrawing, guiding and cooling the primary product,which has partially solidified in the permanent mold and has a liquidcore and a solidified strand shell, characterized in that the submergednozzle includes outlet openings (8) which lie opposite one another andin the operating position are directed toward the narrow side walls (4,5) of the permanent mold, in that the internal dimensions of thepermanent mold at the level of the lateral outlet openings of thesubmerged nozzle substantially correspond to the dimensions of theprimary product, and in that the width (b) of the submerged nozzle andthe height (h) of the lateral outlet opening of the submerged nozzle arefixed in relation to a defined width:thickness ratio of the primaryproduct or the permanent mold in such a way that the followingconditions$\frac{h}{B} = {{\frac{9}{5}\psi} + {\frac{1}{5}\frac{D}{B}}}$

and $\frac{b}{h} = {1.9 - 2.0}$

are fulfilled and a numerical ratio ψ which sets the relationshipbetween the velocity of the molten material in the core cross section ofthe submerged nozzle (v_(k)) to the casting rate (v_(c)) is determinedaccording to the following condition$\psi = {0.1\left( \frac{B}{D} \right)^{- 0.7}}$

in which: B=width of the primary product or of the permanent mold (mm)D=thickness of the primary product or of the permanent mold (mm) b=widthof the submerged nozzle (mm) h=height of the lateral outlet opening ofthe submerged nozzle (mm) ψ=numerical ratio (no dimensions).
 7. Thecontinuous-casting plant as claimed in claim 6, characterized in thatthe primary product or the permanent mold has a width:thickness ratio$\frac{B}{D} = {15 - 25.}$


8. The continuous-casting plant as claimed in claim 6, characterized inthat the primary product or the permanent mold has a width:thicknessratio $\frac{B}{D}$

of approximately
 20. 9. The continuous-casting plant as claimed in oneof claims 6 to 8, characterized in that the inner base (9) of thesubmerged nozzle is designed to be inclined from the center of thesubmerged nozzle toward the outlet opening (8) in the casting direction.10. The continuous-casting plant as claimed in claim 9, characterized inthat the inclination of the inner base (9) of the submerged nozzle isfrom 10° to 20°, preferably approximately 15°.
 11. A submerged nozzlefor use in a continuous-casting plant for producing a continuously castprimary product, in particular broad slabs, having a thickness of theprimary product D>100 mm and a width of the primary product B=2700 mm to3500 mm at a casting rate of v_(c)<2 m/min, this continuous-castingplant having a permanent mold (1), which is formed by wide side walls(3, 4) and narrow side walls (5, 6) and into which the submerged nozzle(6) projects in operation, characterized in that the submerged nozzlehas lateral outlet openings (8) which lie opposite one another, and acontinuous inner base (9), in that the internal dimensions of thepermanent mold at the level of the lateral outlet openings (8) of thesubmerged nozzle substantially correspond to the dimensions of theprimary product, in that the width (b) of the submerged nozzle and theheight (h) of the lateral outlet opening of the submerged nozzle arefixed in relation to a defined width:thickness ratio of the primaryproduct or the permanent mold in such a way that the followingconditions$\frac{h}{B} = {{\frac{9}{5}\psi} + {\frac{1}{5}\frac{D}{B}}}$

and $\frac{b}{h} = {1.9 - 2.0}$

are fulfilled and a numerical ratio ψ which sets the relationship of thevelocity of the molten material in the core cross section of thesubmerged nozzle (v_(k)) to the casting rate (v_(c)) is determinedaccording to the following condition$\psi = {0.1\left( \frac{B}{D} \right)^{- 0.7}}$

in which: B=width of the primary product or of the permanent mold (mm)D=thickness of the primary product or of the permanent mold (mm) b=widthof the submerged nozzle (mm) h=height of the lateral outlet opening ofthe submerged nozzle (mm) ψ=numerical ratio (no dimensions).
 12. Thesubmerged nozzle as claimed in claim 11, characterized in that the innerbase (9) of the submerged nozzle (6) is designed to be inclined from thecenter of the inner base toward the outlet opening.
 13. The submergednozzle as claimed in claim 12, characterized in that the inclination ofthe inner base (9) of the submerged nozzle is 10° to 20°, preferablyapproximately 15°.
 14. The submerged nozzle as claimed in one of claims11 to 13, characterized in that there are only two outlet openings (8)which are of substantially rectangular design.